Investigation of the Effect of NACA 4416 Aerofoil Shaped Fuselage on the Performance of an Unmanned Air Vehicle

Abstract

The piloted aircraft were predominantly used for surveillance and reconnaissance missions but the vast technological improvements in anti-aircraft weapons, interceptor aircraft coupled with the high cost of state of the art aircraft and crew training led to the development of UAVs. Operation of UAV proved to be easy and adaptable for a variety of tasks. Recent advancement in technology made it possible to use low cost fixed wing UAVs for many applications like surveillance and reconnaissance for law enforcement and homeland security, scientific data gathering, forest fire monitoring, geological survey etc. As such, a lot of researches on the performance of UAVs are presently on going in many laboratories of the world but not that much as yet carried out in Bangladesh. UAVs mostly fly under low speed conditions. The aerodynamic characteristics of the UAVs have many similarities than that of the monoplane configuration. Research on UAV configurations has been carried out mostly in the developed countries but sufficient research data on enhancement of performance is not readily available to extend further research in this area. Due to the UAV’s potential for carrying out so many tasks without direct risk to the crew or humans, they are ideal for testing new concepts which have been put forward as means to further increase the vehicle’s capability and performance. The present work will contain the design and fabrication of two different UAV models – one is having aerofoil shaped fuselage and another one is conventional cylindrical shaped fuselage. The volume of both the models has been kept same. The air flow over the aerofoils is incompressible and subsonic. NACA 4416 aerofoil profile and CFD software have been used extensively for those design. 2D NACA 4416 profile has also been designed by CFD software and investigated to compare the result with different configurations. This thesis briefly explains the detail design procedure of both the models. The fabricated models has been tested in AF 100 wind tunnel. This thesis investigates the aerodynamic characteristics of both the models at two different velocities (20 m/s and 40 m/s respectively) and at different VI angle of attack from -3° to 18°. The stalling angle for both the designs is found at about 15° theoretically and 14° experimentally. The lift and drag forces obtained from computational result is found more than that of the experimental result. UAV requires higher lifting force with a smaller size. The fuselage of UAV might be a good source of lifting force. As such, the performance of development of all lifting vehicle technology like aerofoil shaped fuselage has been investigated thoroughly during carry out research on small sized UAV. This thesis will also analyze the flow pattern for both the models. Static pressure distribution on upper and lower surfaces of the wings for both the design has been investigated and analyzed. The difference in suction and positive pressure of aerofoil shaped fuselage is found more in comparison with the cylindrical shaped fuselage model. The difference in pressure has been increased for aerofoil shaped fuselage at 40 m/s than that has been obtained at 20 m/s. Out of four parameters (25%, 50%, 75% and 90% from the root of the wing), the maximum difference in suction and positive pressure is found at 25% from the root of the wing for both the designs. The difference in suction and positive pressure has been reduced from root towards tip of each wing. The maximum difference in suction and positive pressure is found at 25% from the root of the wing of “Aerofoil shaped fuselage at 40 m/s” than other three configurations. The difference in suction and positive pressure is found maximum within 12 to 15% of chord length for all type of configurations. The „aerofoil shaped fuselage configuration‟ at both 20 and 40 m/s provides extra lift from it’s fuselage due to it’s aerofoil shape than that of the „conventional cylindrical shaped fuselage‟ configuration. But this model has produced some extra drag due to it’s increased fuselage frontal area, fuselage-wing interference effect and trailing edge vortex. The effect of fuselage frontal area is found minimum due to smaller size of UAV. The fuselage-wing interference effect has been reduced here by selecting the up wing blended type model. After thorough investigation, finally it is revealed that the aerofoil shaped fuselage would be a good option for designing the future UAV.